1. Field of the Invention
The present invention relates to an alignment device intended for use in combination with ophthalmic cylinder surfacing machines to determine proper mechanical adjustments in that machine for grinding ophthalmic lenses.
2. Description of the Prior Art
Ophthalmic laboratories utilize cylinder surfacing machines for the purpose of grinding ophthalmic lenses in accord with the prescription written by ophthalmologist and optometrists. While such cylinder surfacing machines do not constitute a part of the present invention, their mode of operation is critical to full and complete understanding of the scope of this invention. These cylinder surfacing machines basically comprise a lap table used to hold the lap blank, which will determine the curve to be ground. Disposed above this lap is a movable pin holder into which a lens is inserted for surfacing in accord with the prescription. In order to grind the proper prescription, it is absolutely necessary that the pin holder be properly aligned with respect to the lap table.
The present state of the art calls for a manual/visual alignment of this crucial relationship. The operator places a metal block in the lap table. He then places a second metal block of the same width on top of the first. The second block has a groove in it to accept the pin holder pins. If the two blocks look or feel parallel, he assumes that the machine is aligned.
Another prior art method calls for the use of a single block having a V-groove formed on one face thereof and parallel to the block's longer sides. The operator places the block in the lap table with the V-groove up. If the pin holder pins do not fit into the V-groove, the pin holder is loosened and manually adjusted. In short, this method calls for just a visual determination.
It should be obvious that such a mechanical alignment verification is, at best, approximate. In fact, misalignment of a few thousandths of an inch is virtually impossible to detect utilizing this present method, and such misalignment will result in the preparation of a lens which is not in accord with the written prescription. This results in an expensive waste of lens material and operator time.
It is obvious, then, that there is a great need in the art for a device capable of insuring proper alignment of cylinder surfacing machines with a high degree of accuracy. Such a device should be of relatively simple construction so as to be easily used by the machine's operator. It should, of course, be durable, and it should require virtually no maintenance. Of perhaps greatest importance, is the necessity that the alignment device provide a readily identifiable signal to the operator that the cylinder surfacing machine is properly aligned.